I want to provide additional information per each indexed document during index time.
And access this information in the same analyzer during query time to compare it.
So. Theoretically it would be great to write this value into some field present in this document and at query time search this field also.
f.e. I have an animals db. I want to find all documents with 3 words 'dog' inside. (just an example). I can setup for my "animals" field my custom BaseTokenFilterFactory which will produce my custom TokenFilter which will just count all 'dog' words and store this number somewhere. So. Where I can store this value to access it at searching time?
Your example sounds like something which will be better suited to be handled by custom Similarity or a query function in Solr and not as a custom analyzer.
For example if using Solr 4.0 you can use the function termfreq(field,term) to order by the number of times dog appears. or you can use it as a filter like so:
fq={!frange l=3 u=100000}termfreq(animals,"dog")
This will filter all documents whose animals field doesn't have at least 3 occurrences of the word dog.
The advantage of using this method is that you don't affect the scoring of the documents only filter them.
The ability to filter by function exists since Solr 1.4 so even if you are using an earlier version of Solr (>1.4) you can easily write the "termfreq" function query yourself
Related
I'm following this tutorial on how to perform indexing on sample documents using Solr. The default collection is "gettingstarted" as shown. Now I'm trying to query it. There are 52 entries as shown:
However, when I replace the q argument with say electronics, it should return 14 results. However, I get nothing.
When I replace the query string q with cat:electronics, then I actually get the 14 results. But why is this the case? isn't q=word supposed to search for word wherever it appears?
No, it's not. Your assumption that:
isn't q=word supposed to search for word wherever it appears?
is wrong. If you're using word as your only query, and nothing more - you're searching for word in the default search field. It does not search all available fields in all available documents.
Also be aware that the default query parser assumes that your query is in the Lucene Query Syntax. To handle more "natural" querying, you can use the edismax query parser. This query parser supports the qf parameter that tells Solr which fields to search, instead of having to use the cat:electronics syntax. Your example would then be q=electronics&qf=cat.
In the example documents you've given, qf=series_t author name cat is probably a decent value to search all these fields for the given query. You can also append ^<weight> to a field name to give hits in the different fields different weights. qf=name^10 cat would give a hit in name ten times the weight of a hit in the cat field.
I would like to implement relevance feedback in Solr. Solr already has a More Like This feature: Given a single document, return a set of similar documents ranked by similarity to the single input document. Is it possible to configure Solr's More Like This feature to behave like More Like Those? In other words: Given a set of documents, return a list of documents similar to the input set (ranked by similarity).
According to the answer to this question turning Solr's More Like This into More Like Those can be done in the following way:
Take the url of the result set of the query returning the specified documents. For example, the url http://solrServer:8983/solr/select?q=id:1%20id:2%20id:3 returns the response to the query id:1 id:2 id:3 which is practically the concatenation of documents 1, 2, 3.
Put the above url (concatenation of the specified documents) in the url.stream GET parameter of the More Like This handler: http://solrServer:8983/solr/mlt?mlt.fl=text&mlt.mintf=0&stream.url=http://solrServer:8983/solr/select%3Fq=id:1%20id:2%20id:3. Now the More Like This handler treats the concatenation of documents 1, 2 and 3 as a single input document and returns a ranked set of documents similar to the concatenation.
This is a pretty bad implementation: Treating the set of input documents like one big document discriminates against short documents because short documents occupy a small portion of the entire big document.
Solr's More Like This feature is implemented by a variation of The Rocchio Algorithm: It takes the top 20 terms of the (single) input document (the terms with the highest TF-IDF values) and uses those terms as the modified query, boosted according to their TF-IDF. I am looking for a way to configure Solr's More Like This feature to take multiple documents as its input, extract the top n terms from each input document and query the index with those terms boosted according to their TF-IDF.
Is it possible to configure More Like This to behave that way? If not, what is the best way to implement relevance feedback in Solr?
Unfortunately, it is not possible to configure the MLT handler that way.
One way to do it would be to implement a custom SearchComponent and register it to a (dedicated) SearchHadler.
I've already done something similar and it is quite easy if you look a the original implementation of MLT component.
The most difficult part is the synchronization of the results from different shard servers, but it can be skipped if you do not use shards.
I would also strongly recommend to use your own parameters in your implementation to prevent collisions with other components.
Imagine an index like the following:
id partno name description
1 1000.001 Apple iPod iPod by Apple
2 1000.123 Apple iPhone The iPhone
When the user searches for "Apple" both documents would be returned. Now I'd like to give the user the possibility to narrow down the results by limiting the search to one or more fields that have documents containing the term "Apple" within those fields.
So, ideally, the user would see something like this in the filter section of the ui after his first query:
Filter by field
name (2)
description (1)
When the user applies the filter for field "description", only documents which contain the term "Apple" within the field "description" would be returned. So the result set of that second request would be the iPod document only. For that I'd use a query like ?q=Apple&qf=description (I'm using the Extended DisMax Query Parser)
How can I accomplish that with Solr?
I already experimented with faceting, grouping and highlighting components, but did not really come to a decent solution to this.
[Update]
Just to make that clear again: The main problem here is to get the information needed for displaying the "Filter by field" section. This includes the names of the fields and the hits per field. Sending a second request with one of those filters applied already works.
Solr just plain Doesn't Do This. If you absolutely need it, I'd try it the multiple requests solution and benchmark it -- solr tends to be a lot faster than what people put in front of it, so an couple few requests might not be that big of a deal.
you could achieve this with two different search requests/queries:
name:apple -> 2 hits
description:apple -> 1 hit
EDIT:
You also could implement your own SearchComponent that executes multiple queries in the background and put it in the SearchHandler processing chain so you only will need a single query in the frontend.
if you want the term to be searched over the same fields every time, you have 2 options not breaking the "single query" requirement:
1) copyField: you group at index time all the fields that should match togheter. With just one copyfield your problem doesn't exist, if you need more than one, you're at the same spot.
2) you could filter the query each time dynamically adding the "fq" parameter at the end
http://<your_url_and_stuff>/?q=Apple&fq=name:Apple ...
this works if you'll be searching always on the same two fields (or you can setup them before querying) otherwise you'll always need at least a second query
Since i said "you have 2 options" but you actually have 3 (and i rushed my answer), here's the third:
3) the dismax plugin described by them like this:
The DisMaxQParserPlugin is designed to process simple user entered phrases
(without heavy syntax) and search for the individual words across several fields
using different weighting (boosts) based on the significance of each field.
so, if you can use it, you may want to give it a look and start from the qf parameters (that is what the option number 2 wanted to be about, but i changed it in favor of fq... don't ask me why...)
SolrFaceting should solve your problem.
Have a look at the Examples.
This can be achieved with Solr faceting, but it's not neat. For example, I can issue this query:
/select?q=*:*&rows=0&facet=true&facet.query=title:donkey&facet.query=text:donkey&wt=json
to find the number of documents containing donkey in the title and text fields. I may get this response:
{
"responseHeader":{"status":0,"QTime":1,"params":{"facet":"true","facet.query":["title:donkey","text:donkey"],"q":"*:*","wt":"json","rows":"0"}},
"response":{"numFound":3365840,"start":0,"docs":[]},
"facet_counts":{
"facet_queries":{
"title:donkey":127,
"text:donkey":4108
},
"facet_fields":{},
"facet_dates":{},
"facet_ranges":{}
}
}
Since you also want the documents back for the field-disjunctive query, something like the following works:
/select?q=donkey&defType=edismax&qf=text+titlle&rows=10&facet=true&facet.query=title:donkey&facet.query=text:donkey&wt=json
Is it possible to boost a document on the indexing stage depending on the field value?
I'm indexing a text field pulled from the database. I would like to boost results that are shorter over the longer ones. So the value of boost should depend on the length of the text field.
This is needed to alter the standard SOLR behavior that in my case tends to return documents with multiple matches first.
Considering I have a field that stores the length of the document, the equivalent in the query of what I need at indexing would be:
q={!boost b=sqrt(length)}text:abcd
Example:
I have two items in the DB:
ABCDEBCE
ABCD
I always want to get ABCD first for the 'BC' query even though the other item contains the search query twice.
The other solution to the problem would be ability to 'switch off' the feature that scores multiple matches higher at query time. Don't know if that is possible either...
Doing this at index time is important as the hardware I run the SOLR on is not too powerful and trying to boost on query time returns with OutOfMemory Exception. (Even If I could work around that increasing memory for java I prefer to be on the safe side and implement the index the most efficient way possible.)
Yes and no - but how you do it depends on how you're indexing your documents.
As far as I know there's no way of resolving this only on the solr server side at the moment.
If you're using the regular XML based interface to submit documents, let the code that generates the submitted XML add boost=".." values to the field or to the document depending on the length of the text field.
You can check upon DIH Special Commands which has a $docBoost command
$docBoost : Boost the current doc. The value can be a number or the
toString of a number
However, there seems no $fieldBoost Command.
For you case though, if you are using DefaultSimilarity, shorter fields are boosted higher then longer fields in the Score calculation.
You can surely implement your own Simiarity class with a changed TF (Term Frequency) and LengthNorm Calculation as your needs.
I implemented Solr SpellCheck Component based on the document from http://wiki.apache.org/solr/SpellCheckComponent , it works good. But i am trying to filter the spell check result based on some other filter. Consider the following schema
product_name
product_text
product_category
product_spell -> copy string from product_name and product_text . And tokenized using white space analyzer
For the above schema, i am trying to filter the spell check result based on provided category. I tried querying like http://127.0.0.1:8080/solr/colr1/myspellcheck/?q=product_category:160%20appl&spellcheck=true&spellcheck.extendedResults=true&spellcheck.collate=true . Spellcheck results does not consider the product_category:160
Is it because the dictionary was build for all the categories? If so is it a good idea to create the dictionary for every category?
Is it not possible to have another filter condition in spellcheck component?
I am using solr 3.5
I previously understood from the SOLR-2010 issue that filtering through the fq parameter should be possible using collation, but it isn't, I think I misunderstood.
In fact, the SpellCheckComponent has most likely a separate index, except for the DirectoSolrSpellChecker implementation. It means the field you select is indexed in a different index, which contains only the information about that specific field you chose to make spelling corrections.
If you're curious, you can also have a look how that additional index looks like using luke, since it's of course a lucene index. Unfortunately filtering using other fields isn't an option there, simply because there is only one field there, the one you use to make spelling corrections.